Electrically heatable glow plug and method for manufacturing an electrically heatable glow plug

ABSTRACT

An electrically heatable glow plug and a method of manufacturing an electrically heatable glow plug allow better decoupling between a heating coil and a combustion-chamber-side end of a glow tube. The electrically heatable glow plug for internal combustion engines includes a metallic glow tube, sealed on the combustion-chamber side, into which an electrically conductive heating coil is introduced, the heating coil being connected in an electrically conductive manner to the glow tube in the region of the sealed combustion-chamber-side end of the glow tube. A sealing arrangement is provided which seals the glow tube on the combustion-chamber side and supports the heating coil and only protrudes into the heating coil if the heating coil is connected to the sealing arrangement via an inner side of the heating coil, for which purpose the sealing arrangement is in contact with the inner side of the heating coil essentially over the entire length protruding into the heating coil.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of prior application U.S. Ser. No.10/250,757 filed Dec. 16, 2003, which was a National Stage Applicationof PCT International Application No. PCT/DE02/04096.

FIELD OF THE INVENTION

The present intention is directed to an electrically heatable glow plugand a method for manufacturing an electrically heatable glow plug.

BACKGROUND INFORMATION

An electrically heatable glow plug for internal combustion engines,which includes a glow element having a corrosion-resistant sealed metalsheath, a filling contained therein made of an electricallynon-conductive, compressed powder, and an electrically conductiveheating coil and regulating coil embedded in the filling, is referred toin German Patent Application No. 197 56 988. In this case, one end ofthe heating coil is welded in an electrically conductive manner to thetip of the metal sheath.

The heating coil has been provided with multiple centering turns on itscombustion-chamber side. The turns are then inserted into acorresponding hole on the combustion-chamber-side end of the glow tube.Subsequently, the heating coil is welded directly to the glow tube onthe combustion-chamber-side end of the glow tube and the glow tube isthus sealed. A TIG welding method (tungsten-inert gas) may be used forthis purpose.

The disadvantage of this technique may be that the number of turns ofthe heating coil welded to the glow tube is not defined. As a result,the resistance of the heating coil varies and therefore both the heatingcharacteristic and the temperature of the glow plug vary.

If the heating coil and the glow tube are made of different materials,the further disadvantage may result that two different materials must bewelded to one another on the combustion-chamber-side end of the glowtube. This results in the glow tube and the heating coil losing theiroriginal properties due to the mixing of the two materials in the weldedregion. The glow tube may crack at this point during continuousoperation of the glow plug. Air then enters the glow tube. This mayresult in oxidation of the heating coil material and the regulating coilmaterial and therefore inevitably in the malfunction of the glow plug.

A rod glow plug, which includes a glow tube, an internal heating coil,and possibly a regulating coil and a connection terminal leading intothe glow tube, is referred to in European Patent Application 1 030 111.The coils are connected to the connection terminal and to the tip of theglow tube. A stabilizing rod is provided, which extends during anassembly step from the connection terminal up to the tip of the glowtube, and possibly into or through an opening in the tip of the glowtube. The stabilizing rod runs essentially centrally through the coils.

SUMMARY OF THE INVENTION

The electrically heatable glow plug according to the present inventionand the exemplary method of manufacturing an electrically heatable glowplug according to the present invention include a sealing arrangement toseal the glow plug on the combustion-chamber side and supports theheating coil. It only protrudes into the heating coil if the heatingcoil is attached to the sealing arrangement via an inner side of theheating coil. For this purpose, in this case the sealing arrangement isin contact with the inner side of the heating coil essentially over theentire length protruding into the heating coil. In this manner, theheating coil is not connected directly to the glow tube, but ratherindirectly via the sealing arrangement. Therefore, the procedures ofsealing the glow tube and of connecting the heating coil to the glowtube in an electrically conductive manner may be separated from oneanother. The glow tube is then sealed by the sealing arrangementindependently of the heating coil, so that the sealing procedure of theglow tube has no influence on the resistance of the heating coil. Thisresistance may be set significantly more exactly by definitelyconnecting the heating coil to the sealing arrangement beforehand, i.e.,before introduction of the heating coil into the glow tube, theconnection of the heating coil to the sealing arrangement only servingfor the electrical contact between the heating coil and the sealingarrangement, but has no sealing function.

A further advantage is that a stabilizer rod is not necessary, so thatmaterial and assembly costs are saved.

Advantageous refinements of the exemplary glow plug and the exemplarymethod of manufacturing the glow plug according to the present inventionare described herein.

An especially precisely set resistance of the heating coil is obtainedif the heating coil is connected to the sealing arrangement by at leastone defined welded point. A somewhat more stable connection between theheating coil and the sealing arrangement, also having higher precisionof the resulting resistance of the heating coil, is obtained if theheating coil is connected to the sealing arrangement by a continuousweld seam. A defined resistance of the heating coil may also be set bycrimping the heating coil to the sealing arrangement, this connectiontechnique being especially simple and simultaneously saving material andenergy.

It may be especially advantageous if the sealing arrangement is ametallic sealing arrangement, in particular from the same material asthe glow tube. If the sealing arrangement is produced from the samematerial as the glow tube, different materials do not have to be weldedwhen the glow tube is sealed, so that the glow tube is much moreresistant to cracks at this point during long-term operation of the glowplug. This has a positive effect on the corrosion properties of the glowtube tip, since the tip does not include a component of the heating coilmaterial. The glow plug according to the present invention therefore mayhave a significantly increased service life.

It may be advantageous if the sealing arrangement is implemented as acap which covers the glow tube on the combustion-chamber side andsimultaneously has an elevation on the glow tube side which receives theheating coil. In this manner, the heating coil may be placed as farforward as possible in the region of the combustion-chamber side tip ofthe glow tube, so that the point of most intense heating extends asclose as possible to the tip of the glow tube.

A further advantage results if the sealing arrangement has a pin on thecombustion-chamber side which protrudes into an opening of the glow tubeon the combustion-chamber side and seals it, and if the sealingarrangement includes a base on the glow tube side in which the heatingcoil is embedded. In this manner, the glow tube may be sealed in anespecially simple, stable, and permanent manner on thecombustion-chamber side.

It may be especially advantageous if the base has a first projection onthe glow tube side which protrudes into the heating coil and is incontact with the inner side of the heating coil on thecombustion-chamber-side end. The position of the heating coil is definedprecisely in this manner.

It may also be advantageous if the base itself protrudes into theheating coil and is in contact with the inner side of the heating coilon the combustion-chamber-side end. In this manner, the material for aprojection on the base on the glow tube side may be saved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first exemplary embodiment of a glow plug according tothe present invention.

FIG. 2 shows a second exemplary embodiment of a glow plug according tothe present invention.

FIG. 3 shows a third exemplary embodiment of a glow plug according tothe present invention.

FIG. 4 shows a fourth exemplary embodiment of a glow plug according tothe present invention.

FIG. 5 shows a fifth exemplary embodiment of a glow plug according tothe present invention.

DETAILED DESCRIPTION

In FIG. 1, 1 identifies a glow plug, which is implemented as asheathed-element glow plug, for example, and includes a plug body 85.Plug body 85 includes a thread 90 to be screwed into a cylinder head ofan internal combustion engine. A glow tube 10 is pressed into plug body85 on the combustion-chamber side. On the combustion-chamber side, glowtube 10 includes a heating coil 15 and a regulating coil 95 adjoiningit, which is connected to heating coil 15. Glow tube 10 protrudes on thecombustion-chamber side into a combustion chamber 5 of the cylinder headin the region of heating coil 15. Regulating coil 95 is in contact witha terminal stud 100, which protrudes out of plug body 85 on the enddistal from the combustion chamber and may be connected to a positiveterminal of the vehicle battery.

Terminal stud 100 and glow tube 10 are sealed in plug body 85 againstenvironmental influences by a sealing ring 105. On the end distal fromthe combustion chamber, plug body 85 has a hexagon 110, with the aid ofwhich the glow plug may be screwed into the cylinder head and/orunscrewed from the cylinder head using a torque tool. A double seal 115seals the inside of plug body 85 from environmental influences on theend of plug body 85 distal from the combustion chamber and an adjoininginsulating disk 116 electrically insulates plug body 85 from terminalstud 100. Sealing ring 105 also electrically insulates terminal stud 100from plug body 85. Sealing ring 105 and double seal 115, as well asinsulating disk 116, are made of a plastic or elastomer, for example.

Double seal 115 and insulating disk 116 are fixed via a round nut 117,or alternatively a round plug. Round nut 117 or the round plug may bescrewed and caulked or only caulked. Insulating powder filling made ofmagnesium oxide, for example, which electrically insulates heating coil15 and regulating coil 95 from glow tube 10, is poured into glow tube10.

The combustion-chamber-side end of glow tube 10 is identified in FIG. 1with reference number 20. In this case, glow tube 10 is implemented astubular and is terminated on the end distal from the combustion chamberby terminal stud 100 and sealing ring 105. On the combustion-chamberside, glow tube 10 is sealed by a sealing arrangement 25. Inside glowtube 10, sealing arrangement 25 supports heating coil 15. Glow tube 10is implemented as a metallic glow tube. Sealing arrangement 25 is alsoimplemented as a metallic sealing arrangement. In this case, sealingarrangement 25 and glow tube 10 may be made of the same metal. Theconnection between sealing arrangement 25 and glow tube 10 may beimplemented by a welded connection, for example. Plug body 85 is alsoimplemented as a metallic plug body.

In this manner, sealing arrangement 25, glow tube 10, and plug body 85form an electrical reference potential, the vehicle frame, for example.If terminal stud 100 is connected to the positive terminal of thevehicle battery, a current flows through regulating coil 95 and heatingcoil 15 via terminal stud 100 up to the vehicle frame. In this manner,heating coil 15 is heated and heats glow tube 10 in combustion chamber 5in order to initiate the combustion process. Regulating coil 95 is madeof a material having a resistance which has a positive temperaturecoefficient, a cobalt-iron alloy, for example. Heating coil 15 is madeof a material having an electrical resistance which is as independent oftemperature as possible. Heating coil 15 may be made of aniron-chromium-aluminum alloy, for example. Due to the fact that heatingcoil 15 is embedded in sealing arrangement 25, an electricallyconductive connection between heating coil 15 and sealing arrangement 25is ensured.

Heating coil 15 may be connected to sealing arrangement 25 by one ormore weld points. Alternatively, heating coil 15 may be connected tosealing arrangement 25 by a continuous weld seam. In anotheralternative, heating coil 15 may be connected to sealing arrangement 25by crimping. In all three cases, a precisely defined number of turns ofheating coil 15 may be connected to sealing arrangement 25 and toproduce a precisely defined electrical resistance of heating coil 15 inthis manner. As shown in FIG. 1, precisely one turn, specifically thelast turn of heating coil 15 facing combustion chamber 5, is connectedto sealing arrangement 25, while the remaining turns of heating coil 15are not connected to sealing arrangement 25 and therefore produce theelectrical resistance of heating coil 15.

Heating coil 15 is thus not connected directly to glow tube 10, butrather is connected indirectly via sealing arrangement 25. No portionsof heating coil 15 are therefore present in the welded connectionbetween sealing arrangement 25 and glow tube 10.

Since the welded connection between sealing arrangement 25 and glow tube10 now does not contain any portions of heating coil 15, it should beless susceptible to nitridation and corrosion, so that no cracks mayarise in the region of this welded connection, which might in turnresult in air and gas penetrating into the inside of glow tube 10 andtherefore also to heating coil 15 and to regulating coil 95. Therefore,glow plug 1 has a significantly longer service life and has a preciselydefined resistance of heating coil 15.

Sealing arrangement 25 may, of course, be made of a different materialthan glow tube 10. However, this material is not to include the materialof heating coil 15, in order to prevent the above-describedsusceptibility to corrosion and nitridation in the welded connectionbetween sealing arrangement 25 and glow tube 10.

The welded connection between sealing arrangement 25 and glow tube 10may be implemented by a TIG welding method (tungsten-inert gas), forexample. The welding of heating coil 15 to sealing arrangement 25, if awelded connection is provided here, may be performed using an especiallyprecise laser welding method, for example, since a reliable electricalconnection is especially important here.

Since the seal of glow tube 10 by sealing arrangement 25 and the weldedconnection described between sealing arrangement 25 and glow tube 10 areproduced independently of heating coil 15, they also have no influenceon the resistance of heating coil 15. The different welds resultingbetween sealing arrangement 25 and glow tube 10 then no longer have aneffect on the resistance of heating coil 15, since they are completelyembedded in sealing arrangement 25. For this purpose, the region inwhich heating coil 15 is embedded in sealing arrangement 25 is separatedcompletely from the region in which sealing arrangement 25 is connectedand/or welded to the glow tube. This should apply to all of theexemplary embodiments described here.

In the first exemplary embodiment shown in FIG. 1, sealing arrangement25 is implemented as a cap which completely covers glow tube 10 on thecombustion-chamber side. On the glow tube side, sealing arrangement 25includes an elevation 30, in the form of one or more pins or acontinuous ring, for example. Outer side 35 of elevation 30 is incontact with an inner wall 40 of glow tube 10. Heating coil 15 isembedded in inner side 45 of elevation 30. For this purpose, it issufficient if the last turn of heating coil 15, which faces combustionchamber 5, is clamped in elevation 30, which is facilitated particularlyif an annular elevation is used. In addition, this turn of heating coil15 may also be welded to elevation 30 by a continuous weld seam orindividual, small, defined welding points, using a laser welding method,for example.

In this manner, the region of the connection of sealing arrangement 25to glow tube 10 is separated from the region where heating coil 15 isembedded in sealing arrangement 25, as required. Through the arrangementshown in FIG. 1, heating coil 15 is brought very close to thecombustion-chamber-side end of sheathed-element glow plug 1, so that thepoint of most intense heating of heating coil 15 and therefore of glowtube 10 protrudes as far as possible into combustion chamber 5.

During assembly of sheathed-element glow plug 1, heating coil 15 isfirst connected on the combustion-chamber side to sealing arrangement 25in the manner described and subsequently introduced, in the direction ofthe arrow as shown in FIG. 1, into glow tube 10 from thecombustion-chamber-side end of glow tube 10 together with sealingarrangement 25 and regulating coil 95, which is attached to heating coil15 on the end distal from the combustion chamber, until sealingarrangement 25 presses against the combustion-chamber-side end of glowtube 10. Subsequently, sealing arrangement 25 is connected to glow tube10 by welding, for example.

During the welding of sealing arrangement 25 to glow tube 10, heatingcoil 15 and regulating coil 95 may be held centered in relation to glowtube 10 on the end of glow tube 10 distal from the combustion chamber bya suitable support device. In this manner, contact of heating coil 15and regulating coil 95 with glow tube 10 is avoided and centeredattachment of terminal stud 100 to regulating coil 95 is made possible.During the welding of sealing arrangement 25 to glow tube 10, these twoparts may be rotated by 360 degrees in order to achieve a uniform weldseam. In FIG. 1, sheathed-element glow plug 1 is shown in a longitudinalsection. In this case, sealing arrangement 25 and glow tube 10 may beconfigured to be rotationally symmetric.

A second exemplary embodiment of sheathed-element glow plug 1 accordingto the present invention is shown in FIG. 2, identical reference numbersidentifying identical elements as in FIG. 1. In this case, only acombustion-chamber side section of glow tube 10 is shown for reasons ofclarity, again as a longitudinal section. In contrast to the firstexemplary embodiment shown in FIG. 1, in the second exemplary embodimentshown in FIG. 2, glow tube 10 is not completely open on itscombustion-chamber-side end 20, but rather has only a comparativelysmall opening 55, which is implemented as a bore hole, for example. Thebore hole is positioned approximately on the combustion chamber tip ofglow tube 10.

Sealing arrangement 25 is implemented as a plug, which has a pin 50 onthe combustion-chamber side, in this exemplary embodiment. Pin 50protrudes into combustion chamber opening 55 of glow tube 10 and sealsit completely. On the glow tube side, sealing arrangement 25 includes abase 60 whose diameter is greater than the diameter of opening 55 and inwhich heating coil 15 is embedded. In this case as well, heating coil 15is first connected to regulating coil 95 and sealing arrangement 25.Regulating coil 95 is also distal from the combustion chamber and iscaulked to terminal stud 100, as shown in FIG. 1. Subsequently, thearrangement thus formed is introduced as shown by the direction of thearrow in FIG. 2, with sealing arrangement 25 in front, into glow tube 10via the opening of glow tube 10 distal from the combustion chamber,until pin 50 protrudes into opening 55 of glow tube 10. Subsequently,pin 50 of sealing arrangement 25 is welded to glow tube 10 in the regionof opening 55.

In this case as well, the glow tube may be rotated by 360 degrees duringthe welding process while pin 50 of sealing arrangement 25 is insertedin opening 55. The TIG welding method may be used again. This principleof the attachment of sealing arrangement 25 to glow tube 10 is also thebasis of the further exemplary embodiments, which are described in thefollowing. They differ only in the attachment of heating coil 15 to abase 60. Thus, base 60 according to the second exemplary embodimentshown in FIG. 2 includes a first projection 65, which protrudes intoheating coil 15 and is in contact with inner side 70 of heating coil 15on its combustion-chamber-side end.

In this case, as shown in FIG. 2, only the last turn of heating coil 15on the combustion-chamber side is again connected to first projection65. Base 60 has a larger diameter than first projection 65 in this case,so that the last turn of heating coil 15 on the combustion-chamber sidealso rests on base 60 and heating coil 15 is therefore separatedcompletely by base 60 from the welded connection to be formed betweenpin 50 and glow tube 10. A component of the heating coil material isthus again prevented from being contained in the connection between pin50 and glow tube 10, i.e., between sealing arrangement 25 and glow tube10. A direct connection between heating coil 15 and glow tube 10 isavoided in this manner, so that the advantages connected therewith,which have already been described, are achieved.

The material for sealing arrangement 25 may be selected in accordancewith the first exemplary embodiment shown in FIG. 1. The connection ofheating coil 15 to sealing arrangement 25 may also be produced, as inthe first exemplary embodiment, by one or more welded points, by acontinuous weld seam, or by crimping the combustion-chamber-side end ofheating coil 15 to first projection 65.

Therefore, a precisely defined connection of only the lastcombustion-chamber side turn of heating coil 15 to sealing arrangement25, for example, and therefore a precisely defined resistance of heatingcoil 15, may also be implemented in the second exemplary embodimentshown in FIG. 2. Of course, the connection may also include more thanone turn of heating coil 15, but in any case it includes a preciselydefined number of turns, which may be predetermined and implementedexactly. In this case, a thread may be provided on the first projectionfor screwing on heating coil 15.

A third exemplary embodiment is shown in FIG. 3, in which identicalreference numbers identify identical elements as in the precedingexemplary embodiments. As described, the connection of sealingarrangement 25 to glow tube 10 is identical in the third exemplaryembodiment to that in the second exemplary embodiment shown in FIG. 2.Only the attachment of heating coil 15 to base 60 is different. As shownin FIG. 3, base 60 includes a second projection 75 on the glow tubeside, which encloses outer side 80 of a defined number of turns ofheating coil 15 on its combustion-chamber-side end. In this manner,heating coil 15 may be attached identically to the first exemplaryembodiment shown in FIG. 1, base 60 and second projection 75 notcontacting glow tube 10 laterally as shown in FIG. 3.

In the third exemplary embodiment shown in FIG. 3, as in the secondexemplary embodiment shown in FIG. 2, heating coil 15 is also separatedfrom glow tube 10 by base 60 of sealing arrangement 25, whose diameteris larger than the diameter of heating coil 15 and which enclosesheating coil 15 through second projection 75. In this case, secondprojection 75 may be implemented similarly to elevation 30 of the firstexemplary embodiment shown in FIG. 1.

A fourth exemplary embodiment of the present invention is shown in FIG.4, in which identical reference numbers again identify identicalelements as in the preceding figures. In this case, the connectionbetween sealing arrangement 25 and glow tube 10 is implemented in thesame manner as in the second exemplary embodiment shown in FIG. 2. Onlythe attachment of heating coil 15 to base 60 is different. In this caseas well, the diameter of base 60 is larger than the diameter of pin 50,as in the second and third exemplary embodiments, so that base 60projects completely beyond pin 50 on the glow tube side. In this case,base 60 itself protrudes into heating coil 15 and is in contact withinner side 70 of heating coil 15 on the combustion-chamber-side end.

Therefore, in the fourth exemplary embodiment, base 60 assumes thefunction of first projection 65 in the second exemplary embodiment, sothat a projection for the attachment of heating coil 15 may be dispensedwith. The last turn of heating coil 15 on the combustion-chamber siderests on glow tube 10 in this case, but outside opening 55 having pin50, so that during welding of pin 50 to glow tube 10 in opening 55, nomaterial of heating coil 15 is included in the welded connection, andheating coil 15 is separated completely by base 60 from the weldedconnection between pin 50 and glow tube 10 in this manner.

In the fourth exemplary embodiment shown in FIG. 4, the last two turnsof heating coil 15 on the combustion-chamber side are connected to base60 by one or more welded points, by a continuous weld seam, or bycrimping or a screw joint, for example. A defined, predeterminedresistance of heating coil 15 may also be set in this manner. In thefourth exemplary embodiment shown in FIG. 4, heating coil 15 may bepositioned as far as possible into the region of the tip of glow tube10, so that the point of most intense heating of glow tube 10 protrudesas much as possible into combustion chamber 5.

A fifth exemplary embodiment is shown in FIG. 5, in which identicalreference numbers again identify identical elements as in the precedingexemplary embodiments. In this case, the connection between sealingarrangement 25 and glow tube 10 is identical to that in the secondexemplary embodiment shown in FIG. 2 and only the attachment of heatingcoil 15 to base 60 is achieved differently. In the fifth exemplaryembodiment shown in FIG. 5, heating coil 15 merely rests on base 60 onthe glow tube side, and is therefore separated from the connectionbetween pin 50 and glow tube 10 by base 60, whose cross-section islarger than that of pin 50, so that no portion of the heating coilmaterial may enter the welded connection of pin 50 to glow tube 10.

The connection between heating coil 15 and base 60 is now again producedon the last combustion-chamber side turn of heating coil 15 by one ormore welded points or a continuous weld seam. In this manner, theresistance of heating coil 15 may be set to a defined, predeterminedvalue. In this embodiment, as in the fourth embodiment shown in FIG. 4and the second embodiment shown in FIG. 2, no elevation and noprojection of sealing arrangement 25 is attached between heating coil 15and the lateral wall of glow tube 10.

Sealing arrangement 25 only protrudes into heating coil 15 for the casein which heating coil 15 is attached to sealing arrangement 25 via innerside 70 of heating coil 15, for which sealing arrangement 25 is incontact with inner side 70 of heating coil 15 essentially over theentire length protruding into heating coil 15.

1. An electrically heatable glow plug for an internal combustion engine,comprising: a metallic glow tube, which is closed on thecombustion-chamber side, and into which an electrically conductiveheating coil is introduced, the heating coil being connected in anelectrically conductive manner to the metallic glow tube in a region ofa closed, combustion-chamber-side end of the metallic glow tube; and asealing arrangement to seal the glow tube on the combustion-chamber sideand to support the heating coil, and being arranged to only protrudeinto the heating coil if the heating coil is connected to the sealingarrangement via an inner side of the heating coil, for which purpose thesealing arrangement is, in this case, essentially in contact with theinner side of the heating coil over an entire length protruding into theheating coil.
 2. The glow plug of claim 1, wherein the heating coil isconnected to the sealing arrangement by one of at least one weldedpoint, a continuous welded seam, a screw joint, and a crimping.
 3. Theglow plug of claim 1, wherein the sealing arrangement is at least one ofmetallic and of a same material as the glow tube.
 4. The glow plug ofclaim 1, wherein the sealing arrangement is welded to the glow tube. 5.The glow plug of claim 1, wherein the sealing arrangement includes a capto cover the glow tube on the combustion-chamber side and includes aglow-tube-side elevation to receive the heating coil.
 6. The glow plugof claim 1, wherein the sealing arrangement includes acombustion-chamber side pin that protrudes into a combustion-chamberside opening of the glow tube and seals it, and the sealing arrangementincludes a glow-tube-side base to receive the heating coil.
 7. The glowplug of claim 6, wherein the heating coil rests on the base.
 8. The glowplug of claim 6, wherein the base includes a first projection on theglow-tube side, which protrudes into the heating coil and is in contactwith the inner side of the heating coil on the combustion-chamber-sideend.
 9. The glow plug of claim 6, wherein the base itself protrudes intothe heating coil and is in contact with the inner side of the heatingcoil on the combustion-chamber-side end.
 10. The glow plug of claim 6,wherein the base includes a second projection on the glow tube side,which encloses the outside of the heating coil on itscombustion-chamber-side end.
 11. A method for manufacturing anelectrically heatable glow plug for an internal combustion engine, themethod comprising: introducing an electrically conductive heating coilinto a glow tube, wherein, before introduction of the heating coil intothe glow tube, which is initially open on its combustion-chamber-sideend, the heating coil is first connected on its combustion-chamber-sideend to a sealing arrangement, the sealing arrangement only protrudinginto the heating coil if the heating coil is attached to the sealingarrangement via an inner side of the heating coil, for which purpose thesealing arrangement is essentially in contact with the inner side of theheating coil over the entire length protruding into the heating coil;and after introduction of the heating coil, together with the sealingarrangement positioned on the combustion-chamber side, into the glowtube, sealing the glow tube on its combustion-chamber-side end by thesealing arrangement.
 12. The glow plug of claim 1, wherein the glow plugis a sheathed-element glow plug.